Smoking compositions

ABSTRACT

A non-volatile source of ketone to flavor tobacco smoke is provided by a β-ketocarboxylic acid ester of a sugar or related compound. The ester is applied to the smoking material and remains in place until the burning coal releases the ketone.

BACKGROUND OF THE INVENTION

This invention relates to an improved smoking tobacco product and themethod of making the same, and more particularly to an improved smokingtobacco product having incorporated therein aroma and flavor-producingadditives which improve the smoking characteristics thereof.

There has been continuing interest in using organic material which canfunction as flavoring agents for modifying or improving the flavor andaroma of tobaccos, foodstuffs, beverages and other such consumerproducts.

It is been established that ketones are natural components of tobaccosmoke, and that they most probably are contributors to tobacco smokeflavor. Further, it has been disclosed in the patent literature thataddition of ketones to tobacco results in an improvement in the flavorof smoking compositions as perceived by test panels.

U.S. Pat. No. 3,174,485 discloses the addition of p-methylacetophenoneto tobacco and food stuffs as a means of providing flavor or flavorenhancement. Other patents which disclose the use of aromatic ketonesinclude U.S. Pat. No. 3,605,760 for 3,5-dialkyl-2-hydroxyacetophenoneand U.S. Pat. No. 3,389,706 for 5-methyl-2-acetylfuran.

Aliphatic ketones have also been found to be useful tobacco additives.U.S. Pat. No. 3,174,485 describes the use of geranylacetone and6-methyl-5-hepten-2-one as tobacco additives, whereas U.S. Pat. No.4,103,036 discloses 1-(3,3-dimethylcyclohexyl)-4-methylpentanone as atobacco additive. Canadian Pat. No. 895,916 describes the synthesis of1-acetyl-3-isopropylcyclopentane and its use to enhance the flavor oftobacco smoke.

Ketoacid esters of menthol were disclosed as tobacco flavorants byMoeller et al in U.S. Pat. No. 3,644,613. Willis discloses diethylα,β-diacetylsuccinate as a flavorant for tobacco, in U.S. Pat. No.4,200,659. Esters of ketoalcohols as tobacco flavors were disclosed byKilburn et al, U.S. Pat. No. 3,403,686.

Sucrose 2,2,4-trimethyl-3-oxovalerate is a beta-ketocarboxylic esterwhich has been described by Wright in U.S. Pat. No. 3,106,477 andproposed as an extender for cellulose esters in film making and thelike.

The present invention provides for the incorporation in tobacco or othersmoking material of a compound which will impart flavors to the smokethereof, which compound is not lost during manufacturing and storage andwhich compound is readily released when the tobacco is smoked.

It is an objective of this invention to permit the incorporation of aketone into a tobacco product in a form which will not be lost oraltered during subsequent manufacturing steps or during storage of thetobacco product.

It is a further objective of this invention to permit the incorporationof a material in tobacco, which material will release a ketone into thetobacco smoke which results when the tobacco containing said material issmoked.

One of the more specific objects of the present invention is toincorporate ketones in a tobacco product in such a manner that they willnot be released prior to the time that the tobacco product is smoked butwill be readily and efficiently released as the tobacco product issmoked.

DESCRIPTION OF THE INVENTION

In accordance with the present invention, a β-ketoester derivative of acarbohydrate is incorporated in a smoking product. The β-ketoesterderivative of a carbohydrate which may be employed in the presentinvention may be represented by the following formula: ##STR1## where

R₁ is an aliphatic or alicyclic alkyl radical having one to 12 carbonatoms, or an aromatic or aralkyl radical with or without substituents onthe ring or a heterocyclic radical having four to 10 carbon atoms;

R₂ and R₃ are each either a hydrogen or an alkyl radical having one tosix carbon atoms, or an aromatic radical with or without substituents onthe ring or a heterocyclic radical having four to 10 carbon atoms;

R₂ and R₃ can also be joined together to form a cyclic ring structure;and

R₄ is a carbohydrate radical or polyhydroxy alkyl radical.

Illustrative of the R₁, R₂, and R₃ substituents in the formularepresented above are methyl, propenyl, butyl, pentyl, hexenyl,methoxyethyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, furyl,tetrahydrofuryl, phenyl, tolyl, xylyl, benzyl, phenylethyl,hydroxyphenyl, methoxyphenyl, naphthyl, pyridyl, pyridazyl, and thelike.

As noted previously, R₂ and R₃ can be joined together to form analicyclic group such as cyclopentyl, cyclohexyl, cycloheptyl, and thelike.

Illustrative of R₄ substituents in the formula represented above areglucose, mannose, galactose, rhamnose, xylose, galactitol, mannitol,glycerol, methyl glucoside, methyl galactoside, phenyl glucoside, andthe like; and their isopropylidene, ethylidene, and benzylidenederivatives.

A β-ketoester derivative of a carbohydrate corresponding to the formularepresented above is usually solid or a viscous syrup having very lowvolatility. Under normal smoking conditions, or other comparablyintensive localized heating conditions, it pyrolyzes into products, oneof which is a ketone having the following general formula: ##STR2##where R₁, R₂ and R₃ are as represented above for structure I.

A detailed study of the mechanism of release of the flavorful ketones IIfrom β-ketoester I, where R₄ is ethyl, has been reported (W. J. Baileyand J. J. Daly, Jr., J. Org. Chem., 22, 1189 [1957]). In Scheme I, ethylacetoacetate (I, R₁ =CH₃, R₂ =R₃ =H, R₄ =C₂ H₅) first undergoes1,2-elimination at the ethyl ester portion to generate acetoacetic acid(I, R₁ =CH₃, R₂ =R₃ =R₄ =H) and ethene. This is the rate determiningstep and requires high temperature. (The study was conducted at460°-560° C.). The acetoacetic acid then undergoes spontaneousdecarboxylation to generate the ketone, in this case, acetone (II, R₁=CH₃, R₂ =R₃ =H). ##STR3##

When R₄ is a radical derived from a carbohydrate, or polyhydroxycompound, the release of II from I follows the same mechanism, that is,from the ketoester (I, R₄ =carbohydrate or polyhydroxy compound) to theketoacid (I R₄ =H), then to the ketone (II). (Scheme 2, where R', R" andR"' are taken together to form the carbohydrate or polyhydroxy radical.)##STR4##

The major advantage of using a carbohydrate or a polyhydroxy radicalinstead of a simple alkyl radical for R₄ is that pyrolysis takes placeat a lower temperature. The following three carbohydrate derivatives,1,2:5,6-di-O-isopropylidene-3-O-(3-p-methylphenyl-3-oxo)propionyl-α-D-glucofuranose,1,2-O-isopropylidene-3-O-(3-p-methylphenyl-3-oxo)propionyl-α-D-glucofuranoseand 3-O-(3-p-methylphenyl-3-oxo)propionyl-D-glucopyranose, werepyrolysed in a 250° C. oil bath for 5 minutes to produce a 31%, 29% and67% yield of p-methylacetophenone respectively, whereas ethyl3-(p-methylphenyl)-3-oxopropionate remained unchanged.

Another advantage of additives of the present invention over a simplealkyl β-ketoester is that the alkyl esters have a greater tendency todistill. For example, ethyl 3-(p-methylphenyl)-3-oxopropionate has aboiling point of 138°-140°/1.5 mm whereas none of the three carbohydratederivatives named above can be distilled without significantdecomposition.

PREPARATION OF β-KETOESTERS OF CARBOHYDRATE DERIVATIVES

One method of preparing the carbohydrate β-ketoester compounds of thepresent invention is by the reaction of an alkanoate derivative with acarbonyl derivative: ##STR5## where

X=Cl, Br or alkoxy radical

Y=carbohydrate or polyhydroxy radical with most of its hydroxyl groupsprotected;

R₁, R₂, R₃, and R₄ are as previously defined.

The reaction is conducted in the presence of a strong base such asphenyllithium, lithium diisopropylamide, lithium tetramethylpiperidene(LTMP), or alkali metal hydride. The conversion of Y into R₄ can becarried out in a number of different ways depending on the nature ofprotecting groups used, e.g. hydrogenation for benzyl ethers, fluorideion promoted hydrolysis for silyl ethers, and careful acidic hydrolysisfor isopropylidene, benzylidene and ethylidene protecting groups. Thefollowing synthesis of3-O-(3-methylphenyl)-3-oxopropionyl-D-glucopyranose is illustrative.##STR6##

Another method of preparing the carbohydrate β-ketoester compound is bythe reaction of an alkanoate derivative with an aldehyde to give acarbohydrate β-hydroxyester compound followed by oxidation of thehydroxyl group to the ketone. ##STR7##

The first reaction is again conducted in the presence of a strong baseas in the previous method. The second reaction is carried out in thepresence of such oxidizing agents as Jones reagent, pyridiniumdichromate, Collins reagent, dimethyl sulfoxide/oxalyl chloride and thelike. Conversion of Y into R₄ would be as previously indicated.

The preparation and use of these esters for ketone release areillustrated by the following Examples which are not intended to limitthe invention.

EXAMPLE I 1,2:5,6-Di-O-isopropylidene-3-O-acetyl-α-D-glucofuranose(2)

A solution of 13 g 1,2:5,6-di-O-isopropylidene-α-D-glucofuranose (0.05mole) and 20 g pyridine (0.25 mole) in 100 mL of tetrahydrofuran (THF)was cooled to -5° C. A solution of 5 g acetyl chloride (0.06 mole) wasadded dropwise at this temperature over 20 min. The mixture was allowedto warm to room temperature over 1 hour and stirred at this temperaturefor 2 days. The mixture was poured into a chilled aqueous ammoniasolution (10 mL conc. NH₄ OH, 100 mL water and 20 g ice). Methylenechloride (100 mL) was added and the layers were separated. The aqueouslayer was extracted twice with 100 mL of methylene chloride and thecombined organic layer washed with 80 mL each of saturated aqueoussolutions of ammonium chloride, sodium bicarbonate and sodium chloride.The methylene chloride solution was then dried over magnesium sulfate.After removal of solvent by rotary evaporation under vacuum, the crudesolid was recrystallized from hexane to give 14.8 g of product (97%yield), m.p. 60° C. (lit. m.p. 59°-60° C.).

1,2:5,6-Di-O-isopropylidene-3-O-(3-p-methylphenyl-3-oxo)propionyl-α-D-glucofuranose(3)

A solution of lithium tetramethylpiperidine in tetrahydrofuran (THF) wasprepared from 4.7 g (33 mole) of tetramethylpiperidine and 13.2 mL of a2.5M solution of n-butyllithium. The solution was cooled to -70° C. anda solution of 5 g (17 mmole)1,2:5,6-di-O-isopropylidene-3-O-acetyl-α-D-glucofuranose (2) in 20 mLTHF was added. After stirring for 10 minutes, a solution of 2.56 g (17mmole) of p-toluoyl chloride in 5 mL of THF was added. After stirringfor an additional 10 minutes, a 10 mL portion of 20% hydrochloric acidwas added and the mixture allowed to warm to room temperature. Thelayers were separated and the organic layer was washed twice with 50 mLof water. The combined aqueous layer was back extracted once with 150 mLmethylene chloride. The combined organic layers were then washed withsaturated solutions of sodium bicarbonate and sodium chloride and thendried over magnesium sulfate. After removal of solvent by rotaryevaporation under vacuum, the crude solid was recrystallized from hexaneto give 4.8 g of product (69% yield), m.p. 95.5°-97° C.

EXAMPLE II1,2-O-Isopropylidene-3-O-(3-p-methylphenyl-3-oxo)propionyl-α-D-glucofuranose(4)

A mixture of 2 g of 3 (4.8 mmole), 10 mL of water, 40 mL oftetrahydrofuran and 3 mL of concentrated hydrochloric acid was heated at45° under nitrogen with stirring for 8 hours. After cooling to roomtemperature, the mixture was saturated with sodium carbonate. The layerswere separated and the aqueous layer was extracted twice with 25 mL ofether. The combined organic layers were washed twice with 25 mL ofsaturated sodium chloride and then dried over magnesium sulfate. Afterremoval of solvent by rotary evaporation, the crude solid wasrecrystallized from ethyl acetate to give 1.06 g of product (60% yield)m.p. 129.5°-131° C.

EXAMPLE III 3-O-(3-p-Methylphenyl-3-oxo)propionyl-D-glucopyranose (5)

A solution of 9 mL trifluoroacetic acid and 1 mL of water was cooled inan ice bath. A 2 g sample of 3 (4.8 mmole) was added and the mixture wasallowed to warm to room temperature over 1.5 hours. Most of the acid andwater were removed by rotary evaporation. The residue was dissolved in10 mL of ethanol and the residual acid was neutralized with 1 g ofsodium bicarbonate. The inorganic salt was filtered off and the filtratewas evaporated to dryness on a rotary evaporator. The crude solid wasrecrystallized from ethanol/ethyl acetate to give 0.95 g of product (60%yield), m.p. 170°-171° C.

EXAMPLE IV Pyrolysis of ketone-release compounds

About 10 mg each of a sample of 3, 4 and 5 was placed in one of 3 nmrtubes. The tubes were then placed into a 250°±1° C. oil bath for 5minutes. After the tubes were cooled to room temperature, 300 μL ofdeuterated chloroform was added into each tube and a 3 μL aliquot ofeach solution was analyzed by gas chromatography. A standard solution of51.1 mg of p-methylacetophenone (6) in 5 mL of deuterated chloroform wasprepared and a 3 μL aliquot was injected into the gas chromatograph. Thefollowing results were obtained.

    ______________________________________                                        Wt. of Material    Wt. of Product                                                                            Theoretical                                    injected (μg)                                                                          Area   μg       Yield (μg)                                                                         Yield                                  ______________________________________                                        3   97          2.23   9.7       30.9    31%                                  4   95          2.25   9.7       33.5    29%                                  5   109         6.70   29.0      43.0    67%                                  6   30.7        7.08                                                          ______________________________________                                    

The amount of unchanged material in each case was not determined.

EXAMPLE V Pyrolysis of ketone release compound in a helium flow system

About 1 mg sample was accurately weighed into a porcelain boat. The boatwas then placed in a horizontal quartz tube surrounded by a furnace heldat a known temperature. A stream of helium (50 cc/min) flowed throughthe quartz tube to flush the pyrolysate into the injector port of a gaschromatograph. The amount of ketone formed was analyzed against anexternal standard. The results for 3, 4, and 5 are shown in FIG. 1.

I claim:
 1. A smoking product having added thereto a β-ketocarboxylicacid ester of a carbohydrate or of an alkyl polyol.
 2. The smokingproduct of claim 1 wherein the added ester is that of a sugar or sugarglycoside.
 3. The smoking product of claim 1 wherein thebeta-ketocarboxylic acid of the added ester is p-methylbenzoylaceticacid.